Trenchers are used in landscaping to define beds, dig ditches for the bases of walls, allow insertion of edging or irrigation tubing and the like. Landscapers often use trenchers to provide the edging around basic, simple gardens, such as ovals or rectangles. While it has long been known to provide highly elaborate garden plans, such as the formal gardens at Versailles, using a trencher to create these shapes has not been practical because of the difficult of keeping a manually operated trencher precisely on course while digging in a complicated design. Instead, the design has been manually laid out and marked, e.g., with lime, then dug in by hand with a shovel. In addition to landscape uses, trenchers are used by electricians and utilities to install cables or wiring in small trenches in the ground.
Trenchers come in a variety of wheel configurations, including two wheel, three wheel and four wheel. Two wheel trenchers, such as those shown in U.S. Pat. Nos. 6,874,581 and 6,938,699 can be highly steerable in very tight curves, but depend entirely on manual brute force from the operator for steering. Four wheel trenchers such as those shown in U.S. Pat. Nos. 4,195,427 and 4,896,442 may reduce the amount of brute force required for steering, but the four wheel configuration prevents a very tight turning radius. Three wheel trenchers can have a tighter turning radius than four wheel trenchers, but most, such as those shown in shown in U.S. Pat. Nos. 4,503,630 and 5,226,248, are steered from the back. This means the wheels must be off-center from the trenching arbor, since they would fall into the trench of they were in-line with the arbor, and this in turn affects their stability, particularly in very tight turns.
The trencher shown in U.S. Pat. No. 5,964,049 (the first two figures of which are included herein as FIGS. 1 and 2) puts the steering wheel at the front of the trencher in line with the arbor, with the axis of the rear wheels in line with the arbor axis. This allows for a much tighter turning radius than the other designs, as well as stability during tight turns. However, the design as shown in the referenced patent has no drive to the wheels, so motive power still comes from the operator. In addition, the combination of the handle extending at the front of the trencher and the need for the operator to stand in front of the handle to pull the trencher limits the usefulness of the trencher in tight spaces.